1 /* 2 * Copyright (c) 1982, 1986, 1989, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * %sccs.include.redist.c% 11 * 12 * @(#)kern_fork.c 8.8 (Berkeley) 02/14/95 13 */ 14 15 #include <sys/param.h> 16 #include <sys/systm.h> 17 #include <sys/map.h> 18 #include <sys/filedesc.h> 19 #include <sys/kernel.h> 20 #include <sys/malloc.h> 21 #include <sys/proc.h> 22 #include <sys/resourcevar.h> 23 #include <sys/vnode.h> 24 #include <sys/file.h> 25 #include <sys/acct.h> 26 #include <sys/ktrace.h> 27 28 /* ARGSUSED */ 29 fork(p, uap, retval) 30 struct proc *p; 31 void *uap; 32 register_t *retval; 33 { 34 35 return (fork1(p, 0, retval)); 36 } 37 38 /* ARGSUSED */ 39 vfork(p, uap, retval) 40 struct proc *p; 41 void *uap; 42 register_t *retval; 43 { 44 45 return (fork1(p, 1, retval)); 46 } 47 48 int nprocs = 1; /* process 0 */ 49 50 fork1(p1, isvfork, retval) 51 register struct proc *p1; 52 int isvfork; 53 register_t *retval; 54 { 55 register struct proc *p2; 56 register uid_t uid; 57 struct proc *newproc; 58 struct proc **hash; 59 int count; 60 static int nextpid, pidchecked = 0; 61 62 /* 63 * Although process entries are dynamically created, we still keep 64 * a global limit on the maximum number we will create. Don't allow 65 * a nonprivileged user to use the last process; don't let root 66 * exceed the limit. The variable nprocs is the current number of 67 * processes, maxproc is the limit. 68 */ 69 uid = p1->p_cred->p_ruid; 70 if ((nprocs >= maxproc - 1 && uid != 0) || nprocs >= maxproc) { 71 tablefull("proc"); 72 return (EAGAIN); 73 } 74 75 /* 76 * Increment the count of procs running with this uid. Don't allow 77 * a nonprivileged user to exceed their current limit. 78 */ 79 count = chgproccnt(uid, 1); 80 if (uid != 0 && count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) { 81 (void)chgproccnt(uid, -1); 82 return (EAGAIN); 83 } 84 85 /* Allocate new proc. */ 86 MALLOC(newproc, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 87 88 /* 89 * Find an unused process ID. We remember a range of unused IDs 90 * ready to use (from nextpid+1 through pidchecked-1). 91 */ 92 nextpid++; 93 retry: 94 /* 95 * If the process ID prototype has wrapped around, 96 * restart somewhat above 0, as the low-numbered procs 97 * tend to include daemons that don't exit. 98 */ 99 if (nextpid >= PID_MAX) { 100 nextpid = 100; 101 pidchecked = 0; 102 } 103 if (nextpid >= pidchecked) { 104 int doingzomb = 0; 105 106 pidchecked = PID_MAX; 107 /* 108 * Scan the active and zombie procs to check whether this pid 109 * is in use. Remember the lowest pid that's greater 110 * than nextpid, so we can avoid checking for a while. 111 */ 112 p2 = allproc.lh_first; 113 again: 114 for (; p2 != 0; p2 = p2->p_list.le_next) { 115 while (p2->p_pid == nextpid || 116 p2->p_pgrp->pg_id == nextpid) { 117 nextpid++; 118 if (nextpid >= pidchecked) 119 goto retry; 120 } 121 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 122 pidchecked = p2->p_pid; 123 if (p2->p_pgrp->pg_id > nextpid && 124 pidchecked > p2->p_pgrp->pg_id) 125 pidchecked = p2->p_pgrp->pg_id; 126 } 127 if (!doingzomb) { 128 doingzomb = 1; 129 p2 = zombproc.lh_first; 130 goto again; 131 } 132 } 133 134 nprocs++; 135 p2 = newproc; 136 p2->p_stat = SIDL; /* protect against others */ 137 p2->p_pid = nextpid; 138 LIST_INSERT_HEAD(&allproc, p2, p_list); 139 p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */ 140 LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash); 141 142 /* 143 * Make a proc table entry for the new process. 144 * Start by zeroing the section of proc that is zero-initialized, 145 * then copy the section that is copied directly from the parent. 146 */ 147 bzero(&p2->p_startzero, 148 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 149 bcopy(&p1->p_startcopy, &p2->p_startcopy, 150 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 151 152 /* 153 * Duplicate sub-structures as needed. 154 * Increase reference counts on shared objects. 155 * The p_stats and p_sigacts substructs are set in vm_fork. 156 */ 157 p2->p_flag = P_INMEM; 158 if (p1->p_flag & P_PROFIL) 159 startprofclock(p2); 160 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 161 M_SUBPROC, M_WAITOK); 162 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 163 p2->p_cred->p_refcnt = 1; 164 crhold(p1->p_ucred); 165 166 /* bump references to the text vnode (for procfs) */ 167 p2->p_textvp = p1->p_textvp; 168 if (p2->p_textvp) 169 VREF(p2->p_textvp); 170 171 p2->p_fd = fdcopy(p1); 172 /* 173 * If p_limit is still copy-on-write, bump refcnt, 174 * otherwise get a copy that won't be modified. 175 * (If PL_SHAREMOD is clear, the structure is shared 176 * copy-on-write.) 177 */ 178 if (p1->p_limit->p_lflags & PL_SHAREMOD) 179 p2->p_limit = limcopy(p1->p_limit); 180 else { 181 p2->p_limit = p1->p_limit; 182 p2->p_limit->p_refcnt++; 183 } 184 185 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT) 186 p2->p_flag |= P_CONTROLT; 187 if (isvfork) 188 p2->p_flag |= P_PPWAIT; 189 LIST_INSERT_AFTER(p1, p2, p_pglist); 190 p2->p_pptr = p1; 191 LIST_INSERT_HEAD(&p1->p_children, p2, p_sibling); 192 LIST_INIT(&p2->p_children); 193 194 #ifdef KTRACE 195 /* 196 * Copy traceflag and tracefile if enabled. 197 * If not inherited, these were zeroed above. 198 */ 199 if (p1->p_traceflag&KTRFAC_INHERIT) { 200 p2->p_traceflag = p1->p_traceflag; 201 if ((p2->p_tracep = p1->p_tracep) != NULL) 202 VREF(p2->p_tracep); 203 } 204 #endif 205 206 /* 207 * This begins the section where we must prevent the parent 208 * from being swapped. 209 */ 210 p1->p_flag |= P_NOSWAP; 211 /* 212 * Set return values for child before vm_fork, 213 * so they can be copied to child stack. 214 * We return parent pid, and mark as child in retval[1]. 215 * NOTE: the kernel stack may be at a different location in the child 216 * process, and thus addresses of automatic variables (including retval) 217 * may be invalid after vm_fork returns in the child process. 218 */ 219 retval[0] = p1->p_pid; 220 retval[1] = 1; 221 if (vm_fork(p1, p2, isvfork)) { 222 /* 223 * Child process. Set start time and get to work. 224 */ 225 (void) splclock(); 226 p2->p_stats->p_start = time; 227 (void) spl0(); 228 p2->p_acflag = AFORK; 229 return (0); 230 } 231 232 /* 233 * Make child runnable and add to run queue. 234 */ 235 (void) splhigh(); 236 p2->p_stat = SRUN; 237 setrunqueue(p2); 238 (void) spl0(); 239 240 /* 241 * Now can be swapped. 242 */ 243 p1->p_flag &= ~P_NOSWAP; 244 245 /* 246 * Preserve synchronization semantics of vfork. If waiting for 247 * child to exec or exit, set P_PPWAIT on child, and sleep on our 248 * proc (in case of exit). 249 */ 250 if (isvfork) 251 while (p2->p_flag & P_PPWAIT) 252 tsleep(p1, PWAIT, "ppwait", 0); 253 254 /* 255 * Return child pid to parent process, 256 * marking us as parent via retval[1]. 257 */ 258 retval[0] = p2->p_pid; 259 retval[1] = 0; 260 return (0); 261 } 262